If you want to go at it cautiously, use the biggest holds and go for 10 sets of 8 seconds for the first month. Use that month to work on smoothly easing weight onto fingers at the start of a set, and easing weight off fingers at the end of a set. Their also should be very little to no swing once your feet are off the ground.

I dunno how many sessions per week you can personally handle.. that's totally your own call.